CN1836386B - Method for synchronizing a radio communication system divided into radio cells - Google Patents

Abstract

The invention relates to a method for synchronizing a radio communication system that is divided up into radio cells. According to said method, every radio cell comprises one base station each for the radio coverage of a plurality of mobile stations assigned to said radio cell. The base station receives, in addition to mobile station signals of its own radio cell, mobile station signals of neighboring radio cells. The base station determines, on the basis of the mobile station signals received, the number of mobile stations and compares this number with a defined threshold value. When the number determined falls below the threshold value, a first synchronization method for synchronizing the base station and the assigned mobile stations is used, said method corresponding to an assigned transmission standard of the radio communication system. When the threshold value is exceeded, a second synchronization method for synchronizing the base station and the assigned mobile stations is used.

Description

Method for synchronizing a radio communication system divided into radio cells

The invention relates to a method according to the preamble of claim 1 for synchronizing a radio communication system which is divided into radio cells.

In cellular radio communication systems, due to the necessary multiplexing of carrier frequencies, co-channel interference known as “co-channel interference” occurs in adjacent radio cells. In order to reduce this interference, the available carrier frequencies are allocated to individual carrier frequency partial resources. With the aid of the so-called "Frequency Reuse" planning, each carrier frequency sub-resource is thus assigned in each case to a radio cell in such a way that, taking into account the minimum spatial distance of the radio cells, only the minimum co-channel interference.

Such a fixed allocation of carrier frequencies or their transmission resources is thus disadvantageous in particular when an unevenly distributed number of subscribers occurs in adjacent radio cells. The base station of one of the radio cells, the number of subscribers under consideration requiring increased radio coverage, therefore places increased demands on the transmission resources. If a lack of transmission resources ensues, a user requesting a new data transmission in the radio cell under consideration is rejected.

Correspondingly, when the number of subscribers increases, co-channel interference occurs within the radio communication system, which can only be limited to a limited extent due to a "frequency reuse" plan with a defined frequency reuse factor ("frequency reuse factor"). Influence.

An increase in transmission resources, which is implemented, for example, in the case of large gatherings by subsequent introduction of further base stations, cannot be easily achieved with simple means due to increased co-channel interference. Expensive "frequency reuse" planning must be carried out again if necessary.

Especially for mobile radio networks of the cellular structure of the future generation, it is very important to use the so-called "orthogonal frequency division multiplexing", "OFDM" transmission technology for short. Such OFDM mobile radio networks require, for example, high data rates for video transmission, which can be transmitted by means of OFDM transmission technology. In this case, a plurality of so-called subcarrier frequencies are used in parallel with one another for the transmission of the user data stream. A transmission channel with a wider bandwidth is realized by means of a plurality of radio transmission channels having generally the same bandwidth. Such OFDM can again be structured depending on the "frequency reuse" plan to be implemented with respect to co-channel interference.

Wideband radio transmission channels are "time dispersive" and suffer from frequency selective fading, typically requiring complex corrections on the receiving side. In OFDM transmission, the radio transmission channel is divided into a number of narrower sub-channels so that each sub-channel experiences "flat attenuation" rather than frequency selective attenuation, thus enabling very simple, typical "single output ( single-tap)" correction is called possible.

In the simplest case, each of the radio transmission channels is assigned the same modulation scheme and thus the same transmission bit rate. In this case, the associated transmission bit rate is determined as a function of the interference of the individual radio transmission channels. A higher order modulation method is used on the radio transmission channel with less interference than the modulation method used on the radio transmission channel with higher interference. It is thus possible, for example, to carry out a transmission with the required quality of service for each radio transmission channel, taking into account the bit error rate. This OFDM multi-carrier method is known in the context of wired transmission in baseband and is also known as "discrete multitone transmission", or "DMT" for short.

In FIG. 3 a cellular OFDM radio communication system according to the prior art is shown representatively for all mobile radio systems. Three adjacent radio cells FZ1 to FZ3 each have an associated base station BTS01 to BTS03 . Each individual base station of the base stations BTS01 to BTS03 serves a plurality of mobile stations T01 to T12 respectively assigned to a radio cell FZ1 to FZ3 . Here, a total of four carrier frequencies f9 to f12 are assigned to the first base station BTS01 of the first radio cell FZ1 and a total of four carrier frequencies f1 to f4 are assigned to the second base station BTS02 of the second radio cell FZ2 according to the frequency reuse plan, A total of four carrier frequencies f5 to f8 are assigned to the third base station BTS03 of the third radio cell FZ3 exclusively for data transmission.

In the connection direction from the base station to the mobile station called "downlink" DL, each of the carrier frequencies f1 to f12 has seven time slots TS1 to TS7 as transmission resources, while in the direction called "uplink" Each of the carrier frequencies f1 to f12 has five time slots TS1 to TS5 as transmission resources in the direction of connection from the mobile station to the base station in "UL". By way of example, free unused time slots are assigned to carrier frequencies f2 , f7 and f11 and are designated with the letter "F".

FIG. 4 schematically shows the state of the art synchronization of the radio cells FZ1 to FZ3 described in FIG. 3 .

The individual base stations BTS01 to BTS03 are neither frequency nor time synchronized with one another. Vertically, the base station-specific carrier frequency offsets Delta01 to Delta03 are shown for each individual base station BTS01 to BTS03 respectively. These carrier frequency deviations Delta01 to Delta03 are caused for each individual base station BTS01 to BTS03 by individual electrical components of the base station, for example a base station-specific local oscillator. Since the mobile stations T01 to T012 are each synchronized to the associated base stations BTS01 to BTS03 , the base stations BTS01 to BTS03 and the corresponding associated mobile stations T01 to T012 each have a carrier frequency offset from one another by Delta01 to Delta03 .

From US 5,872,774 a synchronization of a "slave base station" to a "reference base station" is known. In this case, the "slave base station" receives the message of the "reference base station" via a mobile station which is located between the two base stations in the so-called "soft handover zone". Synchronization of the "slave base stations" is achieved with the "round trip delay" measurement applied.

A synchronization is known from WO 00/35117 A2 in which the time difference between adjacent base stations is measured directly at the base station under consideration. Relative time differences are determined and eliminated based on previously known base station location coordinates. For the case where it is not possible to directly measure the base station signals of adjacent base stations at the base station under consideration, a "fixed mobile station" is used for forwarding the signals of said base station, said "fixed mobile station" being arranged in a so-called "Soft Handoff Area".

The invention is based on the task of implementing a cellular radio communication system, in particular an OFDM radio transmission system, in such a way that the subscribers operate optimally both at high and low traffic levels, with regard to minimum co-channel interference. The manner in which radio transmission resources are utilized efficiently is covered by the radio.

The object of the invention is achieved by the features of claim 1 . Advantageous refinements are specified in the dependent claims.

According to the invention, the base station determines the number of active mobile stations and compares it with at least one predetermined threshold value. Depending on said threshold or thresholds, a first synchronization method or a second synchronization method is selected or used.

A predetermined threshold is used as a starting point representatively and exemplarily below.

When the number of active mobile stations is low, ie below a predetermined threshold, a first synchronization method is used which is designed according to the transmission standard assigned to the radio communication system. For example, in a UMTS radio communication system, the synchronization of base stations and mobile stations takes place in accordance with the associated UMTS standard.

When the number of active mobile stations is high, ie when a predetermined threshold is exceeded, the second synchronization method described below is used.

In the first synchronization method, a lower number of active mobile stations is assumed than in the second synchronization method, so that in this case there is sufficient transmission capacity for the transmission of synchronization information.

By using the first synchronization method when the number of active mobile stations is small, the required accuracy of synchronization is guaranteed.

By means of the second synchronization method, time synchronization and frequency synchronization in the cellular radio communication system are implemented in a simple manner. Since the second synchronization method dispenses with the transmission of additional signaling information for synchronization, which previously had to be exchanged on a higher protocol layer between the base station and the mobile station, it can be used for carrying out the transmission of useful data. Radio transmission resources remain free.

In the second synchronization method, it is particularly advantageously possible for particularly adjacent base stations to use reserved radio transmission resources, the reserves being commonly assigned to the base stations used for data transmission. This enables particularly efficient radio resource management. A dynamic utilization of available radio transmission resources is introduced or implemented in individual radio cells.

In the second synchronization method, depending on the current traffic load, the available radio transmission resources are allocated optimally in each case, wherein the unevenly distributed user occupation is particularly advantageously balanced.

In the second synchronization method, in a preferred embodiment, the assignment of the radio transmission resources takes place taking into account the interference situation at the radio transmission resources to be selected. It is thus possible, for example, for two adjacent base stations to jointly use a time slot of a carrier frequency as a radio transmission resource at the same time, in order to radio cover a mobile station, as long as the interference situation in the selected time slot permits, wherein the adjacent Each individual base station of the base stations respectively has radio coverage for the mobile stations assigned to it.

The radio transmission resources are determined, for example, by time slots of a commonly assigned carrier frequency.

A dynamic utilization of the available radio transmission resources in the individual radio cells is achieved by means of a second synchronization method which is implemented by signal processing on the receiving side and subsequent adjustment of the synchronization state of the base station or mobile station implement. Depending on the current traffic load, the available radio transmission resources are always optimally allocated. It is particularly advantageous here to equalize the uneven distribution of subscriber occupations in adjacent radio cells.

The second synchronization method enables the application of interference suppression methods on the base station side and/or on the mobile station side, since interference suppression methods are optimized especially for mutually synchronized wanted and interfering signals.

The second synchronization method makes it possible, for example, to easily add additional base stations in the event of large gatherings, or thereby to enable an accompanying change in the number of radio cells.

Both in the first synchronization method and in the second synchronization method, the participating base stations select the radio transmission resources dynamically such that interference with adjacent radio cells or co-channel interference with mobile stations respectively assigned to the adjacent radio cells Interference is minimized.

The method according to the invention is particularly preferably used in an OFDM radio communication system, wherein the OFDM radio communication system is particularly preferably used for services with relatively high data rates.

The method according to the invention consists of applying a selection or synchronization method based on a plurality of thresholds. For example, two thresholds are used to determine the threshold range, whereby a "smooth" selection or switchover between synchronization methods is achieved.

By means of correspondingly configured threshold value ranges, for example, a hysteresis function (hysteresis function) which may be implemented with respect to time can be applied when selecting a synchronization method.

It is particularly advantageous to reduce the influence of occasionally poorly received mobile stations on the selection of the synchronization method.

The second synchronization method will be explained in more detail below with reference to the figures.

Figure 1 shows a second synchronized OFDM radio communication system with the present invention,

Figure 2 shows a second synchronization according to the invention implemented from the base station side of Figure 1,

Figure 3 shows a cellular OFDM radio communication system according to the prior art representatively described in the introduction to the description, and

FIG. 4 shows the synchronization situation according to the prior art described in the introduction to the description.

FIG. 1 schematically shows an OFDM radio communication system with a second synchronization according to the invention for other mobile radio systems.

Three adjacent radio cells FZ1 to FZ3 each have an associated base station BTS1 to BTS3 . Each individual base station of the base stations BTS01 to BTS03 serves a plurality of mobile stations T11 to T33 respectively assigned to a radio cell FZ1 to FZ3 . In this case, a total of four mobile stations T11 to T14 are assigned to the first base station BTS1 for radio coverage, and a total of five base stations T21 to T25 are assigned to the second base station BTS2 for radio coverage. A total of three mobile stations T31 to T33 are assigned to the third base station BTS3 for radio coverage.

All three base stations BTS1 to BTS3 equally use a common carrier frequency resource, which has a total of twelve carrier frequencies f1 to f12, for the transmission of user data. In the connection direction from the base station to the mobile station called "downlink" DL, each of the carrier frequencies f1 to f12 has seven time slots TS1 to TS7 as transmission resources, while in the direction called "uplink" Each of the carrier frequencies f1 to f12 has five time slots TS1 to TS5 as transmission resources in the direction of connection from the mobile station to the base station in "UL". By way of example, free unused time slots are assigned to carrier frequencies f2 , f8 and f12 and are designated with the letter "F".

In contrast to FIG. 3 , here the exclusive assignment of the carrier frequencies f1 to f12 to the base stations or radio cells is eliminated by the second synchronization according to the invention.

Representatively for the second and third radio cells FZ2 and FZ3 , the second synchronization method according to the invention will be explained in detail below. Here, "synchronization" here should be understood as not only the time slot synchronization of the carrier frequency, but also the frequency synchronization of the carrier frequency.

In the uplink UL, the first base station BTS1 of the first radio cell FZ1 receives, in addition to the signals of the mobile stations T11 to T14 assigned to it, additional signals from the mobile stations of the adjacent radio cells FZ2 and FZ3. This reception takes place automatically without additional monitoring of additional frequency bands.

For example, the first base station BTS1 also receives the signals of the mobile stations T21 and T22 of the second radio cell FZ2 and the signals of the mobile stations T31 and T32 of the third radio cell FZ3 in the uplink. Based on the received mobile station signals of the adjacent radio cells FZ2 and FZ3, the first base station BTS1 determines a first time offset and a first frequency offset and derives appropriate time synchronization values and frequency synchronization values from these values, the first The base station BTS1 eventually synchronizes to said synchronization value. This is exemplarily illustrated in FIG. 2 below.

Typically for all mobile stations, note that in the downlink DL the third mobile station T13 of the first radio cell FZ1 receives signals from the adjacent radio cells FZ2 and FZ3 in addition to the signals from the base station BTS1 of the own radio cell FZ1 Signals of base stations BTS2 and BTS3. Based on the received base station signal, the third mobile station T13 then determines the second time offset and the second frequency offset, and derives appropriate time synchronization values and frequency synchronization values from these values, the mobile station T13 finally synchronizes to the sync value.

The second synchronization method according to the invention repeats, for example, in a frame-wise manner, whereby a precise, self-organized time synchronization and frequency synchronization is obtained as a mean over time.

A particularly flexible and adaptively implemented radio resource management is particularly advantageously achieved by means of the second synchronization method, since all base stations have access to a common reserve of radio transmission resources. In this case, the selection of the carrier frequency takes place, for example, taking into account minimal co-channel interference. The allocation of transmission resources to the mobile stations is carried out entirely by the base station to which the respective mobile stations are assigned.

The unique assignment of the canceled carrier frequency to the base station or radio cell makes it possible, for example, that the base station BTS1 for the radio coverage mobile station T14 and the base station BTS1 for the radio coverage The base station BTS3 of the mobile station T32 uses the time slot TS5 of the carrier frequency f5 at the same time. This interference situation is influenced, for example, by sectorized receiving and/or transmitting antennas at the base station, or by the propagation properties of the radio signal, or by the spatial distance between the users, or the like.

In sectorization, a base station for transmitting or for receiving radio signals has, for example, three antenna arrangements, each of which radio covers a sector with an opening angle of 120°. This results in a spatial separation or differentiation of the radio signals and, depending on the selection of the sector opening angle, an improvement in the interference situation.

In the case of an uneven radio cell load, each of the three base stations has full or partial access to the radio resources of the carrier frequency as required, thereby avoiding the simultaneous overloading of individual radio cells in the individual radio cells. Bottlenecks in radio cells. The second synchronization method according to the invention is implemented independently and requires neither expensive signaling nor expensive GPS time synchronization.

FIG. 2 shows on the basis of FIG. 1 a second synchronization method implemented on the part of base station BTS1.

Vertically, the mobile station-specific carrier frequency offset is shown for each individual mobile station. The first base station BTS1 under consideration receives the signals transmitted by the mobile stations T21, T22, T12, T13, T11, T31 and T32 in the uplink direction and determines therefrom a synchronization value d1, which is here exemplarily Ground is shown as the mean value by the hatched rectangle. The base station BTS1 accordingly corrects its synchronization in the direction of a positive synchronization value d1. The same applies to the further base stations BTS2 and BTS3.

In contrast to this, a synchronization of individual mobile stations not described in detail here is achieved.

If the TDMA/FDMA multiple access method is used alone or in combination with each other in a so-called cellular radio communication system and the so-called time-division duplex transmission mode (TDD-Mode) is used for transmission, the signal received at the base station r(t) includes the superposition of a plurality of signals of mobile stations transmitting simultaneously with the FDMA multiple access method of all radio cells.

From the received signal r(t), each base station obtains the averaged reception times of the superimposed OFDM symbols of mobile stations located in adjacent radio cells.

By means of the correction of adjacent sample values arranged at a distance of OFDM symbol length N, a measure λ(k) is formed for sample value k, whose value also has in the case of an FDMA uplink with OFMA symbol length N Periodic value.

have:

$\mathrm{<span\; class="notranslate">\; \&lambda;</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0</span>}}^{\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}\mathrm{<span\; class="notranslate">\; r</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; r</span>}}^{<span\; class="notranslate">\; *</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; N</span>}<span\; class="notranslate">\; )</span>$

In this case, M denotes the window length over which the measured values are averaged for the purpose of noise reduction. This is usually the same length as the so-called "guard gap". Possibly, the length of the interval N of the corrected values of the deviation and the window length M are selected in order to improve the detection characteristics.

Instead of the mean time deviation of the mobile station signal components at the various base stations, the absolute value of the measure |λ(k)| proportional. For this reason, the largest metric absolute value |λ(k)| is found from the calculated metric values, and the position of the largest absolute value continues to be used as an estimate of the time offset for each base station. The metric value is a complex number in the case of the remaining remaining carrier frequency deviation, so that the phase of the signal received in the OFDM symbol can be determined from the phase of the smaller value of the carrier frequency deviation measured in the maximum value of the metric. Approximate value of average carrier frequency deviation.

Advantageously, in order to separate the FDMA signals of different mobile stations, the received signals are evaluated in the frequency domain, since these signals are assigned to different subcarriers. In this case, the carrier frequency deviation is effected in each case as a function of the phase rotation of the OFDM symbols received on each subcarrier.

Here, according to the phase change in the time interval T _s of the transmission factor H(n,k) of the partial carrier frequency k between the subcarriers of two consecutive OFDM symbols with time indices n and n+1 , get the frequency deviation δf(k) of part of the carrier frequency. Thus there are:

$\mathrm{<span\; class="notranslate">\; \&delta;\; f</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&pi;</span>}}<span\; class="notranslate">\; \&angle;</span><span\; class="notranslate">\; \{</span>\frac{\mathrm{<span\; class="notranslate">\; h</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span>}{\mathrm{<span\; class="notranslate">\; h</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; \}</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}}$

From the carrier frequency offset values of the adjacent radio cells present after estimation in the frequency domain, for example an average carrier frequency offset of the mobile stations received from the adjacent radio cells is determined after evaluation according to the quality of the estimation.

The time offsets are respectively determined from the phase rotation between the received OFDM symbols of the mobile stations assigned to the same base station. From the time offset values present after the estimation in the frequency domain, for example an average time offset of mobile stations received from neighboring radio cells is determined after evaluation in terms of the quality of the estimate.

With the aid of the determined time offset and carrier frequency offset, each base station adjusts its own carrier frequency and its own transmission time according to the determined values. In the design of a properly tuned loop loop filter, this process automatically leads to an estimate of convergence.

For the second synchronization method according to the invention, the following steps are required for a base station newly present in a TDD radio communication system:

- Listen uplink and downlink to determine TDD frame structure,

- determination of the absolute transmit time points for all measured receive time points, and

-Analyze the signal according to the pattern described earlier.

On the uplink, each base station determines the useful power of the mobile station active in the radio cell and the co-channel interference power per subcarrier from adjacent radio cells.

Based on this information, each base station makes an independent decision about the bandwidth to occupy. The one with the least interference power is selected. Depending on the available channel quality, the base station makes an adaptive decision regarding the position and number of subcarriers to be occupied and the physical transmission parameters to be used in order to be able to provide optimal radio coverage of the mobile stations located in the radio cell. Interfering with the organization of the community is unnecessary.

Such multiple access avoids interference within a radio cell and between mobile stations in adjacent radio cells. An ad hoc optimization of the dominant cell of the applied multiple access method is carried out. This optimization is carried out taking into account the characteristics of the radio transmission channel and taking into account the instantaneous interference situation in the cellular environment.

Claims (12)

1. be used for being divided into synchronously the method for the radio communications system of radio plot,

-wherein by means of the time division multiple access method transmit data and wherein each radio plot have one and be used for radio and cover a plurality of attaching troops to a unit in the base station of the mobile radio station of described radio plot,

-wherein the base station also receives from the mobile station signal that adjoins radio plot except the mobile station signal of the radio plot that receives self,

Mobile radio station quantity is determined according to described mobile station signal in-wherein said base station, and this mobile radio station quantity and at least one predetermined threshold value are compared,

-wherein when being lower than described at least one threshold value, described mobile radio station quantity is used for synchronous described base station and first method for synchronous of the mobile radio station of being attached troops to a unit, the transmission standard that the corresponding described radio communications system of described first method for synchronous is attached troops to a unit,

-wherein when exceeding described at least one threshold value, described mobile radio station quantity is used for synchronous described base station and second method for synchronous of the mobile radio station of being attached troops to a unit, the base station determines that according to the mobile station signal that is received described base station carries out synchronous time synchronized value and Frequency Synchronization value in view of the above in described second method for synchronous

It is characterized in that,

-when exceeding described at least one threshold value, mobile radio station also receives from the base station signal that adjoins radio plot except receiving the base station signal of self radio plot,

-described mobile radio station determines that according to the base station signal that is received described mobile radio station carries out synchronous time synchronized value and Frequency Synchronization value in view of the above.

2. according to the method for claim 1, it is characterized in that,

The base station of adjoining radio plot makes the radio transmission resources of stand-by storage, and described deposit is attached troops to a unit in the described base station that is used for transfer of data publicly.

3. according to the method for claim 1 or 2, it is characterized in that,

In second method for synchronous, described base station uses the time slot of public carrier frequency of attaching troops to a unit as radio transmission resources.

4. according to the method for claim 1 or 2, it is characterized in that, in second method for synchronous, at least two base stations of adjoining (BTS1, BTS3) simultaneously and jointly use the time slot (TS5) of carrier frequency (f5) to cover the mobile radio station (T14, T32) of being attached troops to a unit separately with radio, and described time slot (TS5) is selected from public radio transmission resources of attaching troops to a unit under the situation of considering the disturbance regime in described time slot (TS5).

5. according to the method for claim 1 or 2, it is characterized in that in second method for synchronous, not only described base station but also described mobile radio station are all adjusted special employed carrier frequency of user and time slot point launch time.

6. according to the method for claim 1 or 2, it is characterized in that, on described base station and/or described mobile radio station, make the cochannel minimum interference by means of disturbance restraining method.

7. according to the method for claim 1 or 2, it is characterized in that, so dispose radio transmission resources, make to be minimized in the cochannel interference of adjoining on the radio plot in base station side.

8. according to the method for claim 1 or 2, it is characterized in that, in described radio communications system, use the OFDM radio transmission method.

9. according to the method for claim 1 or 2, it is characterized in that, in described radio communications system, use TDD or FDD radio transmission method.

10. according to the method for claim 1 or 2, it is characterized in that, in second method for synchronous, determine time deviation by proofreading and correct, and rotate to determine frequency departure by the phase place of after transforming to frequency domain, obtaining continuous symbol.

11. the method according to claim 1 or 2 is characterized in that, implements second method for synchronous, the signaling by means of the higher protocol layer between the base station and the mobile radio station of being attached troops to a unit that need not to add.

12. the method according to claim 1 or 2 is characterized in that, selects described method for synchronous by means of the hysteresis function of being determined by threshold range about the time.

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